1. Field of the Invention
The present invention relates to devices, systems, and processes used in Power Line Network Adapter (PLNA) environments, and more specifically to extending the capability of a Universal Serial Bus (USB) port using power lines and related interfaces.
2. Brief Description of the Related Art
The Universal Serial Bus (USB) is a universal wired interface for serial communications. The USB interface in accordance with version 1.1 of the USB specification is rated at 12 Mbps supporting low-speed and mid-speed data rate applications. Examples of low-speed applications include relatively simple devices such as keyboards, mice, and the like while mid-speed applications include audio and telephony applications and the like. It will further be appreciated that USB v1.1 is capable of handling video transfers on a limited basis provided various parameters such as frame speed and frame size bring the data transfer rate within the physical limitations of the interface. In more recent versions of the USB specification, such as, for example, version 2.0, faster data rates are contemplated on the order of 480 Mbps. Thus, a broader range of peripherals can be used with USB v2.0. The higher speed applications would include digital video and the like.
An exemplary USB configuration is shown in FIG. 1. As can be seen in exemplary scenario 100, the minimum configuration to establish serial communication over a USB interface requires at least host controller 110, such as a processor, intelligent device, or the like, and at least one USB device 130 which can be a device such as a keyboard, mouse, or the like or a generic device often described as a node or hub. It should be appreciated that unlike host controllers, USB device 130 need not be intelligent and may include simple devices such as a speaker. A simple case might include a computer acting as host controller 110 and a USB speaker acting as USB device 130 in a configuration where the speaker needs to be connected to the host. In a typical application, USB compliant cable 120 having a USB compliant plug connector type (not shown), for example to match the corresponding USB jack type (not shown) on at least the host end thereof, is connected between host controller 110 and USB device 130, a speaker for example, and the computer can then send, for example, digital audio signals to the speaker. It is important to note that in FIG. 1 power may be supplied from host 110 to USB device 130 via VBUS 121 and ground 124 lines with data being transferred on D+122 and D−123 lines as would be appreciated by one of ordinary skill in the art.
Problems arise however if a user wishes to put the speaker in a location remote from the host controller. If the distance is great enough, a USB cable will not work due to limitations associated with, for example, maximum wire length. Moreover, even when within maximum wire length, a wire may not be easy or desirable to use when the speaker placement is difficult to reach or in an area where a wire connection spanning between the computer and speaker would be unsightly.
One proposed approach, often referred to as Powerline technology, solves problems associated with connecting remotely located components with wires or cables by transmitting signals for various interfaces over household power lines, for example, by modulating the 110 or 120 VAC, 60 Hz household power supply with information signals. Transmitters and receivers are easily relocated anywhere where a wall outlet is present. One such Powerline standard interface is the HomePlug interface for transmitting data on household power lines. Many suppliers produce devices compliant with, for example, the HomePlug 1.0 standard and include network interfaces typically having a USB device interface and connector. Such interfaces do not address the problems arising in connection with the use of USB connected devices. Conventional USB to Powerline interfaces cannot presently act as virtual extension cords to other USB devices as will be explained in greater detail herein.
Conventional USB extenders are typically configured to provide host-to-host networking with additional latency and layers of protocol overhead via a special USB network operational mode. Alternatively, slave devices and host emulators exist but are limited in that 1) they cannot supply the 5V @ amp required under the USB specifications, and 2) they do not offer full operational capability. The combination of deficiencies associated with 1) and 2) result in devices which are limited in capability and are not USB compliant. A user at a first host desiring to, for example, print at a printer connected to a second host at the other end of a conventionally extended, e.g. host-to-host, Powerline connection must address the printer as a networked printer through the second host. Thus a simple, extended host-to-peripheral device connection is not possible with conventional USB extenders.
Consequently, it would be desirable to provide a device for effectively extending the wire length of a USB connection and allowing, for example, HomePlug technology to extend its usefulness beyond computer networking without adding new wires to a home or business. Such a device should be fully compliant with USB protocol and capable of being certified thereunder.